Substation telephone circuit



Oct. 17, 1933. p 1,930,537

SUBSTATION TELEPHONE CIRCUIT Filed May 4. 1932 mil? Harold C. @15

Patented Oct. 17, 1933 iuNrren STATES carer OFFICE Harold 0.1Pye, Oak Park, Ill, assignor, by mesne assignments, to Associated Electric 7 Laboratories, Inc., Chicago, IlL, a corporation Delaware Application May 4, 1932. Serial No. 609,095

' s Claims. '(cl. na -s1) The. present invention relates to sub'station telephone circuits in general, larly, to substation circuits for conrnoibbattery telephone systems; and one or" the objects of the invention, briefly stated, is to provide a new and improved common-battery, anti-side-tone tele'-- i 2 soever in the usual booster-belhboxe's.

In explanation of this latter object, it maybe said that a great deal of sales resistance has been encountered in the.selling of instruments of the cradle type, both by the manufacturer and by the operating telephone companies, since customers are hesitant about purchasing or renting instruments which are not interchangeable with existing telephone instruments insofar as the bell boxesare concerned, and that, consequently, there is a great need for'an anti-side-tone circuit for cradle-type instruments which can overcome this sales resistance. So far as is known, there is at present, no such anti-sidet one circuit which is commercially practical.

Other objects, not specifically mentioned here, will be apparent fro mthe detailed description .which follows: The drawing, comprising Figs. 1 to 1, inclusive, shows the details of the present invention. Fig. lshows one embodiment of tr e presentinvention; Fig. 2 shcws two modifications or" the arrangement of Fig. 1; Fig. 3 shcws,.in schematic ,form, the talking circuit of Figs. 1 and 2 ;Fig. t shows, in schematic .form, the dialling circuit of Figs. land 2; Fig. 5 shows a second embodiment of this invention and two modifications thereof; Fig. 6 shows the talking circuit of Fig. 5 in schematic form; and 7 shows the dialling circuit of Fig. 5 in schematic form. I

Although the telephone circuits have been provided with calling devices, or impulse senders, for use in automatic telephone systems, it is to be understood that the calling devices may be omitted andthe circuits used to equal advantage 5 in manual telephone systems.

but, more particushown in a broken line form.

Referring in detail to Fig. 1, it will be noted that the bell-box, in which terminates the subscribers line conductors 1 and 2, comprises the usual induction coil I, condenser C, and ringer B. This is the usual booster bell-box in general use. Connected to this bell-box by the cord having the three conductors 3, l, and 5, is the desk stand, or cradle, which is providedwith the usual hook-switch contacts 9 audio, and, in the case of automatic telephone systems, thecalling device S having the impulse springs 11 and shunt springs 12 which perform the well-knownfunctions.

Connected to the desk stand, or cradle, by means of the three-conductor cord 678, is the hand telephone instrument comprising the receiver R and transmitter T. In order to arrange the circuit as anti--side-tcne, the receiver has been provided with the two windings l6 and 17, and the resistance element 13 and condenser have been connected in series with the winding 17- or the receiver. By this means, the transmitter T, being connected tothe junction of the two receiver windings, is shunted by an artificial line comprising winding 17, element 13, and condenser D, the characteristics of which are such as to balance the line 1-2. Thus, it can readily be seen, by reference to Fig. 3 also, that the eiiect of the winding 17 of the receiver R included. in the artificial circuit neutralizes the effect of the other winding 16 of the receiver R upon the receiver diaphragm when any sound waves are picked up by the transmitter T since current is driven in opposite directions through the Windlugs 16 and 1'7. The resistance element 13 and the condenser D are mounted in the hand instrument. As an alternative, the resistance element 13 may be incorporated in the winding 17 of the receiver, and for this reason element 13 has been By providing the proper amount of resistance and reactance in the artificial circuit, the telephone circuit may be made completely anti-sidetone. Inasmuchas it is not commercially practical to balance the artificial network with each line with whicha circuit of this type might be connected, it has been found most satisfactory to balance the artificial network for an average Thus balanced, the telephone circuit'is sufficiently anti-side-tcne under normal conditions for all practical purposes. 5 In one of the-modifications shown in Fig. 2, that represented by the solid lines, the resistance element 13 and condenser D are mounted in the desk stand and the one winding of the :receiver is connected to the resistance element by the additonal conductor 14.

In the second modification in Fig. 2, the resistance element 13 is mounted in the desk stand but the condenser D is omitted and the condenser C in the bell-box used instead by the addition of the conductor 15 to the cord connecting the desk stand with the bell box.

The balancing of the artificial network in the modifications in Fig. 2 is the same as in the embodiment in Fig. l.

The talking and dialling circuits as shown in Figs. 3 and 4, respectively, are substantially identical with and have all of the advantages of the substation telephone circuit shown and described in Patent No. 1,657,635, issued January 31, 1928, to T. G. Martin.

In the embodiment and modifications thereof shown in Fig. 1, a special induction coil 1 is used, in addition to the regular induction coil I, and its use eliminates the second winding on the receiver. The special induction coil I does not .have to be as large as the usual induction coil I since it is not required to carry any direct current. This special induction coil, because of its size, is mounted in the desk stand.

In this embodiment, as in the first embodiment, a separate resistance element 13. can be employed, or else the one winding of the induction coil can be made of higher resistance wire to supply the additional resistance in the artificial network that would be supplied by the element 13. Should it be desired to eliminate the condenser D and use the usual condenser C for the dual purpose, the additional conductor 15, shown as a broken line in Fig. 5, will be added in the cord between the desk stand and the bell box.

In the other modification, in Fig. 5, the condenser D is omitted and the conductor 18, shown dotted, connected to the artificial line 13' in a conductive shunt circuit about the transmitter T.

The talking and dialling circuits in Figs. 6 and 7 are substantially the same as those shown in Figs. 3 and 4. From Fig. 6 it can readily be seen that sound waves picked up by the transmitter T will cause current to be driven in opposite directions through two of the windings of the special induction coil I thereby neutralizing the inductive effect upon the winding to which the receiver is connected.

From theforegoing, it can now be fully appreciated that the telephone circuits herein disclosed overcome the aforementioned objections while providing a circuit for a cradle type telephone which is completely anti-side-tone, which has the well-known advantages of the boostertype circuit, which can be used to equal advantage in both manual and automatic telephone systems, and which, when used in automatic telephone systems, has a dialling circuit previously determined by tests and actual commercial usage to be the best.

The invention having been thus descirbed, what is considered new and is desired to have protected by Letters Patent is detailed in the claims which follow.

What is claimed is:

1. In a common-battery substation telephone including a transmitter, a condenser, and an induction coil, with the transmitter and the condenser connected in, parallel branches of the telephone circuit, and with one winding of the induction coil connected in one branch; a third parallel branch containing an artificial line and a condenser, a magnetic structure having two windings thereon connected one in each condenser branch, said windings being so related to one another that they act in magnetic opposition with respect to current-flow through the two condenser branches in parallel, and a sound-wave producing device controlled by magnetic changes in said structure caused by unbalanced currentflow in said windings.

2. In a common-battery substation telephone including a transmitter, a condenser, and an induction coil, with the transmitter and the condenser connectedin parallel branches of the telephone circuit, and with one winding of the induction coil connected in one of said branches; a third parallel branch containing an artificial line and a condenser, a sound-wave producing device comprising a magnetic structure having two windings connected one in each condenser branch, and a diaphragm magnetically influenced to produce sound waves, said two windings being so related to one another that they act in magnetic opposition with respect to ourrent-flow established in the two condenser a condenser, with the transmitter, on the one hand, and the condenser and one winding of the induction coil, on the other hand, connected in parallel branches of the telephone circuit; a third parallel branch including a condenser, a twowinding receiver having a winding in each con.- denser branch, said condenser branches being so balanced with respect to one another that they act to produce a balanced condition in the receiver whenever current-flow is established through said receiver windings in parallel by the operation of said transmitter, whereby said receiver is rendered inoperative except when an unbalanced condition is produced by the action of said induction coil.

4. Ina common-battery substation telephone circuit wherein the receiver, one winding of the induction coil, and a condenser, on the one hand, and the transmitter, on the other hand, are connected in parallel relationship to the other winding of the induction coil; side-tone prevention means comprising a second winding on the receiver, a resistance element and a condenser serially connected in parallel with said transmitter to said other winding of the induction coil.

5. In a common-battery substation telephone circuit wherein the receiver, one winding of the induction coil, anda condenser; on the one hand, and the transmitter on the other hand, are connected to the other winding of the induction coil in parallel relationship; anti-side-tone means comprising a condenser and a second winding on the receiver contaning an artificial .line, serially connected to said other winding of the'induction coil in parallel with said transmitter.

6. In a substation telephone including a transmitter, an induction coil, and a condenser, with the transmitter and the condenser connected in parallel branches of the telephone circuit, and with one winding of the induction coil connected in one of the branches; a third parallel branch containing a condenser, a three-winding induction coil having a Winding included in each of the two condenser branches, the two windings of the second coil, which are in said condenser branches, being so related to one another that current-flow established through those two windings in parallel by the operation of said transmitter produces equal and opposite effects in the third winding of said second induction coil, and a receiver connected to the third windng of said second coil and operated only when there is an unbalanced condition of current-flow established through said two windings of the second induction coil by action of the first induction coil.

7. In a common-battery substation telephone including a transmitter, an induction coil, and a condenser, with the transmitter and the condenser connected in parallel branches of the telephone circuit, and with one winding of the induction coil connected in one of said branches; a three-Winding induction coil having one winding included in said condenser branch, a third parallel and conductive branch including the second winding of said second induction coil, said third branch and said condenser branch being so balanced with respect to one another that they act to produce a balanced condition with respect to the third winding of the second induction coil how in said windings.

whenever current-flow is established through these two branches in parallel by the operation of the transmitter, and a receiver connected to said third winding and operated only when an unbalanced condition is produced by the currentflow established through said branches by the action of the first-mentioned induction coil.

8. In a common-battery substation telephone including a transmitter, a condenser, an artificial line element, and an induction coil, with the transmitter and said condenser connected in parallel branches of the telephone circuit, and with HAROLD c. PYE. 

